CN112226191B - Biodegradable adhesive and preparation method thereof - Google Patents
Biodegradable adhesive and preparation method thereof Download PDFInfo
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- CN112226191B CN112226191B CN202010855630.2A CN202010855630A CN112226191B CN 112226191 B CN112226191 B CN 112226191B CN 202010855630 A CN202010855630 A CN 202010855630A CN 112226191 B CN112226191 B CN 112226191B
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J175/00—Adhesives based on polyureas or polyurethanes; Adhesives based on derivatives of such polymers
- C09J175/04—Polyurethanes
- C09J175/06—Polyurethanes from polyesters
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/40—High-molecular-weight compounds
- C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
- C08G18/4202—Two or more polyesters of different physical or chemical nature
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- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/40—High-molecular-weight compounds
- C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
- C08G18/4236—Polycondensates having carboxylic or carbonic ester groups in the main chain containing only aliphatic groups
- C08G18/4238—Polycondensates having carboxylic or carbonic ester groups in the main chain containing only aliphatic groups derived from dicarboxylic acids and dialcohols
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- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/40—High-molecular-weight compounds
- C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
- C08G18/4266—Polycondensates having carboxylic or carbonic ester groups in the main chain prepared from hydroxycarboxylic acids and/or lactones
- C08G18/4283—Hydroxycarboxylic acid or ester
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- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
- C09J11/02—Non-macromolecular additives
- C09J11/04—Non-macromolecular additives inorganic
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- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
- C09J11/02—Non-macromolecular additives
- C09J11/06—Non-macromolecular additives organic
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- C08G2230/00—Compositions for preparing biodegradable polymers
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- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
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- C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
- C08K3/20—Oxides; Hydroxides
- C08K3/22—Oxides; Hydroxides of metals
- C08K2003/2237—Oxides; Hydroxides of metals of titanium
- C08K2003/2241—Titanium dioxide
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- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
- C08K3/24—Acids; Salts thereof
- C08K3/26—Carbonates; Bicarbonates
- C08K2003/265—Calcium, strontium or barium carbonate
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- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2201/00—Properties
- C08L2201/06—Biodegradable
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Abstract
The invention discloses a biodegradable adhesive and a preparation method thereof, and the biodegradable adhesive comprises the following components in parts by weight: 1-95 parts of polylactic acid copolymer polyol, 5-95 parts of polyester polyol, 0.1-2 parts of hydrolysis stabilizer, 1-45 parts of inorganic filler, 0.5-2 parts of thixotropic agent and 0-8 parts of curing agent. The biodegradable adhesive prepared by the invention has good biodegradability and controllable relative molecular weight and viscosity, and can be used in the fields of surface bonding of adhesive tapes, stationery, shoe industry, automotive upholsteries, packaging materials and other building or decorative materials and the like.
Description
Technical Field
The invention relates to the technical field of adhesives, in particular to a biodegradable adhesive and a preparation method thereof.
Background
With the increasing attention on environmental protection in the world, particularly, green economy is taken as the main direction of future development in China, and the green environmental protection is the inevitable trend of development of various industries in the future. Adhesives which play a significant role in various industries are bound to face higher environmental protection requirements; the traditional adhesive has the advantages of low cost, good cohesiveness and the like, but the traditional adhesive is difficult to degrade in the natural environment, the content of the waste adhesive in the nature is higher and higher along with the lapse of time, the pollution is more and more serious, and the ecological environment and the human health are affected, so that the biodegradable environment-friendly adhesive becomes a necessary way for the development of the adhesive in a future period of time.
Taking adhesive tapes and express delivery as an example, under the support of huge population in China, the popularization of internet mobile terminals brings about rapid development of the express delivery industry, and since 2014, the business volume of the express delivery industry in China is stably kept in the world for 5 years continuously. Wherein, the number of Chinese average express delivery in 2017 is about 29, the number of Chinese average express delivery in 2018 is about 36, and the number of Chinese average express delivery in 2019 is about 45; in 2018 years only, about 53 hundred million woven bags are consumed in the national express industry, about 245 million plastic bags, about 57 million envelopes, about 143 million packing boxes and about 430 million adhesive tapes are consumed in the national express industry, and the packaging adhesive tapes used in China can be wound around the earth for 1077 circles each year.
The composite material is a new material formed by optimally combining two or more than two material components with different properties by applying an advanced material preparation technology. It can play the advantages of various materials, overcome the defect of single material and enlarge the application range of the material. According to incomplete statistics, related enterprises of the composite materials in China have more than 1 million families, the yield of the composite materials in 2017 and 2018 is close to and exceeds 500 million tons respectively, and the retention amount of the composite materials in China is more than 3400 million tons as long as 2018. According to the measurement and calculation, the existing holding capacity of the composite material in China exceeds 5000 ten thousand tons, and the composite material is still increased by about 10% every year. Because the composite material is optimized by materials with different properties, and a plurality of composite materials are even prepared by 4 to 5 different materials, the recovery technology and the recovery value of the composite material are greatly limited. Taking express corrugated paper as an example, in 2018, the consumption of the express corrugated paper in China reaches 825.4 ten thousand tons, and the corrugated board is a composite board formed by bonding surface paper, lining paper, core paper and corrugated paper processed into corrugated corrugations. In order to improve the strength of corrugated paper and the moisture and mildew resistant effects, the corrugated paper composite board is commonly used by a modified acrylate adhesive at present. The acrylate adhesive has strong pungent smell in the using process, and the biodegradability of the corrugated paper composite board is greatly reduced. The final disposal mode after recycling is usually landfill or incineration, which causes different degrees of environmental impact, and the biodegradable adhesive is adopted to replace the acrylate adhesive, so that after the corrugated paper is recycled, the compost degradation can be directly carried out, the integral degradation period of the corrugated paper is shortened, and the environmental load generated by using the corrugated paper composite material is greatly reduced. Similarly, more and more composite materials are prepared by adopting degradable resins in the future, a large amount of adhesives are needed in the preparation process, when the composite materials are prepared by adopting the degradable resins, higher requirements on the adhesives are necessarily put forward, and the green degradable adhesives are also a trend which is not developed yet.
Chinese patent publication No. CN1288033A discloses a method for preparing a water-soluble biodegradable adhesive based on a mixture of polyaspartic acid or its salt and its derivative with natural thickener resin. However, the method has complex process and higher cost; the prepared adhesive has poor water resistance and solvent resistance. Publication No. CN107177339A discloses a method for preparing a biodegradable adhesive from a lactide chemical synthesis product. However, the adhesive synthesized by the method has poor economy, a solvent is required, and the volatilization of the solvent causes certain pollution. Lando et al, in the literature, introducingLactccd-Based Biodegradable Tissue Adhesives, describe a lactic acid-Based Biodegradable adhesive, which introduces epsilon-caprolactone molecules into the PLA molecular chain, thereby improving the strength of the adhesive, but also increasing the cost.
It is noted that biodegradation is a chemical process in which environmentally available microorganisms convert biodegradable articles into natural substances such as water, carbon dioxide and compost (without the need for artificial additives). However, biodegradation is not possible in any environment, the biodegradation process depends on the surrounding environmental conditions, and the biodegradable articles need to be biodegradable according to the relevant standards, such as in the environment of industrial composting or domestic composting. Thus, when biodegradable articles enter non-standard environments such as the ocean, the biodegradability of these articles is greatly reduced. Taking common PLA as an example, under the condition of industrial composting (the temperature is 58 +/-2 ℃, the humidity is 98 percent and certain microorganisms exist), the weight loss of a PLA sample strip reaches 70 percent in about 50 days, the PLA sample strip can be completely degraded within 3-6 months, but under the condition of simulating natural soil, the weight loss of the PLA sample strip after 1 year is only 0.23 percent, and the degradation is not generated basically; similarly, no significant weight loss was observed for the PLA strips after one year of soaking, regardless of whether they were placed in fresh water or in the ocean, and GPC testing showed no significant change in molecular weight. And after other biodegradable plastics, such as PBAT and PBS are soaked in seawater for one year, the weight loss rate is less than 2 percent, and the degradation is very slow.
Therefore, the adhesive prepared by using PLA molecular chains as main raw materials also has the condition of slow degradation speed in the ocean, and conceivably, when a large amount of the biodegradable adhesive enters the nature or the ocean and can not meet the degradation condition, the biodegradable adhesive still causes great pollution to the environment like other common adhesives, but the biodegradable adhesive prepared by the invention can adjust the degradation speed of the adhesive in the ocean by doping polyglycolic acid chain segments.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a biodegradable adhesive and a preparation method thereof. The biodegradable adhesive has good biodegradability and controllable relative molecular weight and viscosity, and can be used in the fields of surface bonding of adhesive tapes, stationery, shoe industry, automotive upholstery, packing materials and other building or decorative materials and the like.
The technical scheme for solving the problems comprises the following steps: a biodegradable adhesive and a preparation method thereof comprise the following steps:
step 1: under the action of a catalyst, carrying out esterification and polycondensation reaction on lactic acid and a mixture thereof and a polyol compound at the temperature of 140-220 ℃, evaporating most of generated by-product water under normal pressure under the protection of nitrogen, and then removing trace water and redundant polyol compound under vacuum pressure until the acid value of the synthesized product is lower than 5mgKOH/g to obtain polylactic acid copolymer polyol; the reaction time is 4-12 h;
and 2, step: under the action of a catalyst, carrying out esterification and polycondensation reaction on a polybasic acid compound and a polyol compound at the temperature of 140-220 ℃, distilling off most of generated by-product water under normal pressure under the protection of nitrogen, and then removing trace water and redundant polyol compound under vacuum pressure until the acid value of the synthesized product is lower than 5mgKOH/g to obtain polyester polyol; the reaction time is 4-12 h;
and step 3: uniformly mixing polylactic acid copolymer polyol, polyester polyol, a hydrolysis stabilizer, an inorganic filler, a thixotropic agent and a curing agent at the temperature of 80-100 ℃, and then continuing to react for 1-4h to obtain the biodegradable adhesive.
Preferably, the biodegradable adhesive comprises the following components in parts by weight:
1-95 parts of polylactic acid copolymer polyol; 5-95 parts of polyester polyol; 0.1-2 parts of hydrolysis stabilizer; 1-45 parts of inorganic filler; 0.5-2 parts of thixotropic agent; 0-8 parts of curing agent.
Preferably, the biodegradable adhesive comprises the following components in parts by weight:
50-75 parts of polylactic acid copolymer polyol; 10-25 parts of polyester polyol; 0.1-2 parts of hydrolysis stabilizer; 10-20 parts of inorganic filler; 0.5-2 parts of thixotropic agent; 0-5 parts of a curing agent.
Preferably, the mixture of lactic acid and its mixture in step 1 comprises aliphatic alkyd acid, aliphatic lactone.
Preferably, the mixture of lactic acid and its mixture in step 1 comprises one or more of glycolic acid, hydroxybutyric acid, hydroxypentanoic acid, hydroxycaproic acid, butyrolactone, valerolactone.
Preferably, the mixture of lactic acid and its mixture in step 1 comprises glycolic acid.
Preferably, the molar ratio of lactic acid and its mixture in step 1 to the mixture is (0.6-1): (0-0.4).
Preferably, the polyol compound in step 1 includes an aliphatic polyol compound and a polyether polyol.
Preferably, the polyol compound in step 1 includes one or more of ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, 1, 2-butylene glycol, 1, 3-butylene glycol, 1, 4-butylene glycol, pentanediol, neopentyl glycol, hexanediol, isohexylene glycol, trimethylolpropane, pentaerythritol, polyethylene glycol 200, polyethylene glycol 400, polypropylene glycol 400, and polypropylene glycol 800.
Preferably, the aliphatic polyol compound is a polyol with pendant groups.
Preferably, the aliphatic polyol compound includes one or more of 1, 2-propanediol, 1, 3-propanediol, 1, 2-butanediol, 1, 3-butanediol, pentanediol and isohexanediol.
Preferably, the molar ratio of the lactic acid and the mixture thereof to the polyol compound in the step 1 is (1-60): 1; more preferably, the molar ratio of the lactic acid and the mixture thereof to the polyol compound is (5-40): 1.
Preferably, the catalyst in the step 1 comprises one or more of zinc acetate, diethyl zinc, stannous octoate, stannic oxide, stannous chloride, tetrabutyl titanate, antimony trioxide, ethylene glycol antimony and antimony acetate; the dosage is 0.01-2wt% of the mass of the lactic acid and the mixture thereof.
Preferably, the polybasic acid compound in the step 2 is one or more of oxalic acid, malonic acid, succinic acid, adipic acid and terephthalic acid. More preferably, the polybasic acid compound is an aliphatic polybasic acid compound, and comprises one or more of oxalic acid, malonic acid, succinic acid and adipic acid.
Preferably, the polyol compound in step 2 includes an aliphatic polyol compound and a polyether polyol.
Preferably, the polyol compound in step 2 includes one or more of ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, 1, 2-butylene glycol, 1, 3-butylene glycol, 1, 4-butylene glycol, pentanediol, neopentyl glycol, hexanediol, isohexylene glycol, trimethylolpropane, pentaerythritol, polyethylene glycol 200, polyethylene glycol 400, polypropylene glycol 400, and polypropylene glycol 800.
Preferably, the molar ratio of the polybasic acid compound to the polyol compound in the step 2 is 1 (1-2); more preferably, the molar ratio of the polyacid compound to the polyol compound is 1 (1.05-1.3).
Preferably, the catalyst in the step 2 comprises one or more of zinc acetate, diethyl zinc, stannous octoate, stannic oxide, stannous chloride, tetrabutyl titanate, antimony trioxide, ethylene glycol antimony and antimony acetate; the amount of the polybasic acid compound is 0.01-2wt% of the mass of the polybasic acid compound.
Preferably, the hydrolysis stabilizer in step 3 is one or more of bis (2, 6-diisopropylphenyl) carbodiimide, polycarbodiimide, phenyl glycidyl ether, bisphenol a diglycidyl ether, triglycidyl isocyanate, 2' -bis (2-oxazoline), 1, 3-benzene-bisoxazoline and styrene-epoxy resin copolymer.
Preferably, the inorganic filler in step 3 is one or more of quartz powder, aluminum powder, iron powder, talcum powder, titanium dioxide, calcium carbonate and barite powder.
Preferably, the thixotropic agent in the step 3 is one or more of acetylene black, organic bentonite, fumed silica, hydrogenated castor oil and calcium sulfate whisker.
Preferably, the curing agent in the step 3 is one or more of Toluene Diisocyanate (TDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), Hexamethylene Diisocyanate (HDI), an adduct of toluene diisocyanate and trimethylolpropane (TDI-TMP), toluene diisocyanate dimer (TDI dimer), and hexamethylene diisocyanate trimer (HDI trimer).
The invention has the following beneficial effects:
(1) the preparation method of the biodegradable adhesive is simple and easy, has high synthesis efficiency, and provides a technical basis for large-scale production.
(2) The addition of the polyester polyol can adjust the density of polar groups such as ester bonds and the like in the biodegradable adhesive, improve the cohesive force and the cohesive force of the adhesive, greatly improve the adhesive residue performance and the permanent adhesion of the biodegradable adhesive, and ensure that the biodegradable adhesive is suitable for various base materials.
(3) A certain amount of glycolic acid is added into the polylactic acid copolymer polyol for copolymerization, so that the degradation speed of the biodegradable adhesive can be accelerated, the biodegradable adhesive can be degraded under natural soil conditions and in oceans, and then, degradation products serve as degradation promoters to accelerate the degradation of other components.
(4) Solvents are not needed in the preparation and use processes of the biodegradable adhesive, so that the defect that the traditional adhesive needs to be diluted by organic solvents is overcome, and pollution caused by volatilization of the organic solvents is avoided.
In conclusion, the biodegradable adhesive provided by the invention has the significance of environmental protection and wide application prospect, thereby generating great social benefit.
Detailed Description
A biodegradable adhesive and a preparation method thereof comprise the following steps:
step 1: under the action of a catalyst, carrying out esterification and polycondensation reaction on lactic acid and a mixture thereof and a polyol compound at the temperature of 140-220 ℃, evaporating most of generated by-product water under normal pressure under the protection of nitrogen, and then removing trace water and redundant polyol compound under vacuum pressure until the acid value of the synthesized product is lower than 5mgKOH/g to obtain polylactic acid copolymer polyol; the reaction time is 4-12 h;
step 2: under the action of a catalyst, carrying out esterification and polycondensation reaction on a polybasic acid compound and a polyol compound at the temperature of 140-220 ℃, distilling off most of generated by-product water under normal pressure under the protection of nitrogen, and then removing trace water and redundant polyol compound under vacuum pressure until the acid value of the synthesized product is lower than 5mgKOH/g to obtain polyester polyol; the reaction time is 4-12 h;
and step 3: uniformly mixing polylactic acid copolymer polyol, polyester polyol, a hydrolysis stabilizer, an inorganic filler, a thixotropic agent and a curing agent at the temperature of 80-100 ℃, and then continuing to react for 1-4h to obtain the biodegradable adhesive.
Preferably, the biodegradable adhesive comprises the following components in parts by weight:
1-95 parts of polylactic acid copolymer polyol; 5-95 parts of polyester polyol; 0.1-2 parts of hydrolysis stabilizer; 1-45 parts of inorganic filler; 0.5-2 parts of thixotropic agent; 0-8 parts of curing agent. More preferably, the biodegradable adhesive consists of the following components in parts by weight: 50-75 parts of polylactic acid copolymer polyol; 10-25 parts of polyester polyol; 0.1-2 parts of hydrolysis stabilizer; 10-20 parts of inorganic filler; 0.5-2 parts of thixotropic agent; 0-5 parts of curing agent.
Preferably, the mixture of lactic acid and its mixture in step 1 comprises aliphatic alkyd acid, aliphatic lactone. More preferably, the mixture of lactic acid and its mixture in step 1 comprises one or more of glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, butyrolactone, valerolactone, caprolactone. More preferably, the mixture of lactic acid and mixtures thereof in step 1 comprises glycolic acid.
Preferably, the molar ratio of lactic acid and its mixture in step 1 to the mixture is (0.6-1): (0-0.4).
In fact, partial mixture is added into lactic acid for copolymerization, so that the crystallinity of the product can be reduced, the melting point of the product is reduced, and the polylactic acid copolymer polyol is viscous solid at normal temperature when the molecular weight is between 1000 and 6000, thereby keeping good cohesive force.
Glycolic acid is the simplest alkyd structure, polyglycolic acid (PGA) polymerized by the glycolic acid is the simplest straight-chain degradable polyester, ester bonds are dense in structure, and steric hindrance around the ester bonds is small, so that the PGA is particularly easy to degrade due to erosion of water molecules, and the PGA spline is taken as an example and placed in the sea, and after one month, the weight loss of the PGA spline can reach 30%, and the PGA spline can be completely degraded within one year; when the PLA strips are placed in the ocean, the PLA strips have no weight loss basically and the molecular weight of the PLA strips has no change basically in a GPC test after one year. The appropriate amount of glycolic acid is added in the copolymerization process, so that the density of ester bonds in the polylactic acid copolymer polyol can be increased, the steric hindrance around the ester bonds can also be reduced to a certain extent, the biodegradable adhesive is more easily corroded by water molecules to be degraded after being discarded, and the degradation product can be used as a degradation promoter to accelerate the degradation speed of the biodegradable adhesive, so that the biodegradable adhesive can be rapidly degraded in seawater or natural soil.
Preferably, the polyol compound in step 1 includes an aliphatic polyol compound and a polyether polyol. More preferably, the polyol compound in step 1 includes one or more of ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, 1, 2-butylene glycol, 1, 3-butylene glycol, 1, 4-butylene glycol, pentanediol, neopentyl glycol, hexanediol, isohexylene glycol, trimethylolpropane, pentaerythritol, polyethylene glycol 200, polyethylene glycol 400, polypropylene glycol 400, and polypropylene glycol 800. More preferably, the aliphatic polyol compound is a polyol with a pendant group, and comprises one or more of 1, 2-propylene glycol, 1, 3-propylene glycol, 1, 2-butanediol, 1, 3-butanediol, pentanediol and isohexanediol.
In fact, among these diols, diols having an even number of carbon atoms in the main chain, such as ethylene glycol, 1, 4-butanediol, and polyols obtained by reacting lactic acid and mixtures thereof tend to have high crystallinity, are mostly solid at normal temperature, and the final product has low cohesive force at low temperature. When the molecular weight of the polylactic acid copolymer polyol prepared from the polyol with the side chain is between 1000 and 6000, the polylactic acid copolymer polyol is more viscous solid at normal temperature, and the prepared adhesive has excellent low-temperature performance; if the polylactic acid copolymer polyol prepared is wanted to have a certain branched chain, a certain proportion of trimethylolpropane or pentaerythritol can be added in a small amount to increase the binding power of the polylactic acid copolymer polyol, but when the adding amount is too large, the prepared polylactic acid copolymer polyol is solid, so that the binding power is lost; similarly, the addition of the polyether polyol can adjust the viscosity of the polylactic acid copolymer polyol, increase the molecular flexibility and wettability of the polylactic acid copolymer polyol, and further adjust the processing performance of the biodegradable adhesive.
Preferably, the molar ratio of the lactic acid and the mixture thereof to the polyol compound in the step 1 is (1-60): 1; more preferably, the molar ratio of the lactic acid and the mixture thereof to the polyol compound is (5-40): 1. The molecular weight of the polylactic acid copolymer polyol prepared by the method is between 2000-5000, and the polylactic acid copolymer polyol is viscous solid at normal temperature.
Preferably, the catalyst in the step 1 comprises one or more of zinc acetate, diethyl zinc, stannous octoate, stannic oxide, stannous chloride, tetrabutyl titanate, antimony trioxide, ethylene glycol antimony and antimony acetate; the dosage is 0.01-2wt% of the mass of the lactic acid and the mixture thereof.
The reaction equation of lactic acid and polyol in step 1 is as follows:
preferably, the polybasic acid compound in the step 2 is one or more of oxalic acid, malonic acid, succinic acid, adipic acid and terephthalic acid. More preferably, the polybasic acid compound is an aliphatic polybasic acid compound, and comprises one or more of oxalic acid, malonic acid, succinic acid, adipic acid and the like.
Preferably, the polyol compound in step 2 includes an aliphatic polyol compound and a polyether polyol. More preferably, the polyol compound in step 2 includes one or more of ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, 1, 2-butylene glycol, 1, 3-butylene glycol, 1, 4-butylene glycol, pentanediol, neopentyl glycol, hexanediol, isohexylene glycol, trimethylolpropane, pentaerythritol, polyethylene glycol 200, polyethylene glycol 400, polypropylene glycol 400, and polypropylene glycol 800.
Preferably, the molar ratio of the polybasic acid compound to the polyol compound in the step 2 is 1 (1-2); more preferably, the molar ratio of the polyacid compound to the polyol compound is 1 (1.05-1.3). The polyester polyol thus obtained has a molecular weight of between 2000 and 5000.
Preferably, the catalyst in the step 2 comprises one or more of zinc acetate, diethyl zinc, stannous octoate, stannic oxide, stannous chloride, tetrabutyl titanate, antimony trioxide, ethylene glycol antimony and antimony acetate; the amount of the polybasic acid is 0.01-2wt% of the mass of the polybasic acid compound.
The reaction equation of the polybasic acid compound and the polyol compound in step 2 is as follows:
preferably, the hydrolysis stabilizer in step 3 is one or more of bis (2, 6-diisopropylphenyl) carbodiimide, polycarbodiimide, phenyl glycidyl ether, bisphenol a diglycidyl ether, triglycidyl isocyanate, 2' -bis (2-oxazoline), 1, 3-benzene-bisoxazoline and styrene-epoxy resin copolymer.
In fact, ester groups in polyester and polyurethane are easy to hydrolyze after long-term use in a humid environment, particularly, glycolic acid is added into the biodegradable adhesive, so that the hydrolysis speed of the biodegradable adhesive is easier to accelerate, and the hydrolysis stabilizer is added, so that the hydrolysis speed in the daily use process can be inhibited or delayed.
Preferably, the inorganic filler in step 3 is one or more of quartz powder, aluminum powder, iron powder, talcum powder, titanium dioxide, calcium carbonate and barite powder.
In fact, the addition of a small amount of inorganic filler can increase the hardness and heat resistance of the adhesive, reduce the phenomenon of high-temperature adhesive residue, improve the overall performance of the adhesive, and reduce the use cost of the adhesive, but the physical properties are reduced when the use amount is too large, and the operation is difficult when the mixing amount of the inorganic filler is large.
Preferably, the thixotropic agent in the step 3 is one or more of acetylene black, organic bentonite, fumed silica, hydrogenated castor oil and calcium sulfate whisker.
In fact, the addition of a small amount of thixotropic agent, through hydrogen bonds, forms a three-dimensional network structure with the polymer molecules, which increases the viscosity of the adhesive several times to many times, even losing fluidity. However, when construction is carried out, under the action of a certain shearing force, the net structure is destroyed, the viscosity of the system is rapidly reduced, and the coating is convenient. When the shearing force disappears, the three-dimensional network structure is formed again, the viscosity of the system is increased, and therefore the adhesive is prevented from leaking.
Preferably, the curing agent in the step 3 is one or more of Toluene Diisocyanate (TDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), Hexamethylene Diisocyanate (HDI), an adduct of toluene diisocyanate and trimethylolpropane (TDI-TMP), toluene diisocyanate dimer (TDI dimer), and hexamethylene diisocyanate trimer (HDI trimer).
In fact, the curing agents are all polyisocyanate polymers, which contain two or more highly unsaturated isocyanate groups (NCO, formula — N ═ C ═ O), and are therefore chemically very reactive and can react with hydroxyl groups in the polylactic acid copolymer polyols and polyester polyols to form urethanes, thereby organically combining them together; the polyisocyanate containing three or more NCO groups can also realize crosslinking and curing, increase the cohesive force of the adhesive and prevent the occurrence of adhesive residue.
The reaction equation of the curing agent and hydroxyl in the step 3 is as follows:
in the following examples:
the acid value determination method comprises the following steps: weighing 1-3g of polymer polyol, placing the polymer polyol in a three-neck flask, adding 20-30mL of toluene-ethanol (2:1) mixed solution, shaking the triangular flask to completely dissolve the sample, heating the sample if necessary, dropwise adding 1% phenolphthalein indicator, titrating the sample to reddish with 0.1mol/L standard KOH solution, and performing blank test according to the same method while keeping the sample from fading within 30 s.
In the formula:
Vtest ofAssay standard solution volume, mL, consuming KOH;
Vblank spaceBlank standard solution volume consuming KOH, mL;
c is the molar concentration of KOH standard solution, mol/L;
w-sample mass, g;
56.10-molar mass of potassium hydroxide, g/mol.
The GPC analysis method comprises the following steps: polymer polyol was prepared into a solution of 1.0 to 1.5mg/mL in Tetrahydrofuran (THF) and subjected to GPC analysis by gel permeation chromatography. The sample amount per injection into the column was 300. mu.L, the flow rate of the test liquid was 1.0mL/min, and the test temperature was 39 ℃.
The preparation method of the artificial seawater comprises the following steps: 23g NaCl, 9.8g MgCl were added to 1L distilled water2· 6H2O，8.9g Na2SO4·7H2O and 1.2g CaCl2And meanwhile, the pH value of the artificial seawater is adjusted to 8.1.
The coating thickness was measured using a coating thickness gauge.
The raw materials used in the present invention are not particularly limited, and may be those generally available on the market.
To further illustrate the present invention, the present invention will be further described with reference to specific examples.
Example 1:
step 1: adding 168.7g (1.5mol) of lactic acid with the mass concentration of 80%, 15.2g (0.1mol) of glycolic acid with the mass concentration of 50%, 10.4g (0.1mol) of 3-hydroxybutyric acid, 6.8g (0.09mol) of 1, 3-propylene glycol and 0.7g of stannous octoate into a reactor, raising the temperature of an oil bath to 170 ℃ under the protection of nitrogen for reaction for 3 hours, then vacuumizing, gradually increasing the vacuum degree, removing trace water and redundant 1, 3-propylene glycol under reduced pressure, and continuing the reaction for 2 hours at 170 ℃ to obtain viscous polylactic acid copolymer polyol, wherein the molecular weight of the polylactic acid copolymer polyol is 2178 by GPC test;
step 2: 177g (1.5mol) of succinic acid, 120.8g (1.59mol) of 1, 3-propylene glycol and 0.7g of stannous octoate are added into a reactor, under the protection of nitrogen, the oil bath is heated to 175 ℃ for reaction for 3 hours, then the reactor is vacuumized, the vacuum degree is gradually increased, trace water and redundant 1, 3-propylene glycol are removed under reduced pressure, the reaction is continued for 4 hours at 175 ℃ to obtain viscous polyester polyol, and the molecular weight of the polyester polyol is 2816 by GPC test;
and step 3: 70 wt% of polylactic acid copolymer polyol, 10 wt% of polyester polyol, 1 wt% of hydrolysis stabilizer bis (2, 6-diisopropylphenyl) carbodiimide, 14 wt% of inorganic filler talcum powder, 1 wt% of thixotropic agent hydrogenated castor oil and 4 wt% of curing agent Toluene Diisocyanate (TDI) are uniformly mixed at 80 ℃ and reacted for 2 hours to prepare the biodegradable adhesive.
Example 2:
step 1: adding 202.5g (1.8mol) of lactic acid with the mass concentration of 80%, 15.2g (0.1mol) of glycolic acid with the mass concentration of 50%, 31.2g (0.3mol) of 3-hydroxybutyric acid, 6.8g (0.09mol) of 1, 3-propylene glycol, 4g of polypropylene glycol 400(0.01mol) and 0.8g of stannous octoate into a reactor, heating the reactor in an oil bath to 180 ℃ under the protection of nitrogen, reacting for 4 hours, vacuumizing, gradually increasing the vacuum degree, removing trace water and redundant 1, 3-propylene glycol under reduced pressure, continuing to react for 3 hours at 180 ℃ to obtain viscous polylactic acid copolymer polyol, and testing the molecular weight of the polylactic acid copolymer polyol to be 2938 by GPC;
step 2: adding 118g (1mol) of succinic acid, 80.5g (1.06mol) of 1, 3-propylene glycol and 0.6g of stannous octoate into a reactor, heating the reactor in an oil bath to 180 ℃ under the protection of nitrogen for reaction for 4 hours, then vacuumizing, gradually increasing the vacuum degree, reducing the pressure to remove trace water and redundant 1, 3-propylene glycol, continuing to react for 2 hours at 180 ℃ to obtain viscous polyester polyol, and testing the molecular weight of the polyester polyol by GPC (phase-sensitive gel permeation chromatography) to be 2236;
and step 3: 60 wt% of polylactic acid copolymer polyol, 18 wt% of polyester polyol, 1.5 wt% of hydrolysis stabilizer bis (2, 6-diisopropylphenyl) carbodiimide, 17 wt% of inorganic filler calcium carbonate, 1 wt% of thixotropic agent fumed silica and 2.5 wt% of curing agent Toluene Diisocyanate (TDI) are mixed uniformly at 90 ℃ and then react for 2h to prepare the biodegradable adhesive.
Example 3:
step 1: adding 112.5g (1mol) of lactic acid with the mass concentration of 80%, 9.1g (0.06mol) of glycolic acid with the mass concentration of 50%, 29.5g (0.25mol) of 3-hydroxyvaleric acid, 3.8g (0.05mol) of 1, 2-propylene glycol and 0.5g of stannous octoate into a reactor, raising the temperature of an oil bath to 185 ℃ under the protection of nitrogen for reaction for 3 hours, then vacuumizing, gradually increasing the vacuum degree, removing trace water and redundant 1, 2-propylene glycol under reduced pressure, and continuing the reaction for 3 hours at 185 ℃ to obtain viscous polylactic acid copolymer polyol, wherein the molecular weight of the polylactic acid copolymer polyol is 2833 by GPC test;
step 2: 236g (2mol) of succinic acid, 157g (2.07mol) of 1, 2-propylene glycol, 20g (0.05mol) of polyethylene glycol and 0.9g of stannous octoate are added into a reactor, under the protection of nitrogen, the oil bath is heated to 190 ℃ for reaction for 4 hours, then the reactor is vacuumized, the vacuum degree is gradually increased, trace water and redundant 1, 2-propylene glycol are removed under reduced pressure, the reaction is continued for 2 hours at 190 ℃ to obtain viscous polyester polyol, and the molecular weight of the polyester polyol is 3316 by GPC;
and 3, step 3: 65 wt% of polylactic acid copolymer polyol, 12 wt% of polyester polyol, 1 wt% of hydrolysis stabilizer phenyl glycidyl ether, 15 wt% of inorganic filler titanium dioxide, 2wt% of thixotropic agent fumed silica, 5 wt% of curing agent toluene diisocyanate and trimethylolpropane adduct (TDI-TMP) are uniformly mixed at 90 ℃ and react for 2h to prepare the biodegradable adhesive.
Example 4:
step 1: adding 112.5g (1mol) of lactic acid with the mass concentration of 80%, 12.1g (0.08mol) of glycolic acid with the mass concentration of 50%, 9.4g (0.08mol) of 3-hydroxypentanoic acid, 3g (0.04mol) of 1, 2-propanediol and 0.5g of stannous octoate into a reactor, heating the oil bath to 185 ℃ under the protection of nitrogen for reaction for 2 hours, then vacuumizing, gradually increasing the vacuum degree, removing trace water and redundant 1, 2-propanediol under reduced pressure, and continuing the reaction for 4 hours at 185 ℃ to obtain viscous polylactic acid copolymer polyol, wherein the molecular weight of the polylactic acid copolymer polyol is 3011 by GPC test;
step 2: 118g (1mol) of succinic acid, 63g (0.5mol, containing two crystal waters) of oxalic acid, 121.6g (1.6mol) of 1, 2-propylene glycol and 0.9g of stannous octoate are added into a reactor, oil bath is heated to 175 ℃ for reaction for 4 hours under the protection of nitrogen, then the reactor is vacuumized, the vacuum degree is gradually increased, trace water and excessive 1, 2-propylene glycol are removed under reduced pressure, the reaction is continued for 4 hours at 175 ℃ to obtain viscous polyester polyol, and the molecular weight is 2937 by GPC test;
and 3, step 3: 55 wt% of polylactic acid copolymer polyol, 20 wt% of polyester polyol, 1 wt% of hydrolysis stabilizer phenyl glycidyl ether, 18 wt% of inorganic filler titanium dioxide, 2wt% of thixotropic agent organic bentonite, 4 wt% of curing agent toluene diisocyanate and trimethylolpropane adduct (TDI-TMP) are uniformly mixed at 90 ℃ and react for 2h to prepare the biodegradable adhesive.
Example 5:
step 1: adding 112.5g (1mol) of lactic acid with the mass concentration of 80%, 15.2g (0.1mol) of glycolic acid with the mass concentration of 50%, 2.7g (0.03mol) of 2, 3-butanediol, 2g of polyethylene glycol 200(0.01mol) and 0.4g of zinc acetate into a reactor, heating the reactor to 180 ℃ in an oil bath under the protection of nitrogen for reaction for 4 hours, then vacuumizing the reactor, gradually increasing the vacuum degree, removing trace water and redundant 2, 3-butanediol under reduced pressure, and continuously reacting for 3 hours at 180 ℃ to obtain viscous polylactic acid copolymer polyol, wherein the molecular weight of the polylactic acid copolymer polyol is 2987 by GPC test;
step 2: 118g (1mol) of succinic acid, 20.8g (0.2mol) of malonic acid, 115.2g (1.28mol) of 2, 3-butanediol and 0.6g of zinc acetate are added into a reactor, under the protection of nitrogen, the temperature of an oil bath is raised to 185 ℃ for reaction for 4 hours, then the vacuum degree is pumped, the vacuum degree is gradually increased, trace water and redundant 2, 3-butanediol are removed by decompression, the reaction is continued for 3 hours at 185 ℃, viscous polyester polyol is obtained, and the molecular weight is 2863 by GPC;
and 3, step 3: uniformly mixing 50 wt% of polylactic acid copolymer polyol, 25 wt% of polyester polyol, 1 wt% of hydrolysis stabilizer 2, 2' -bis (2-oxazoline), 20 wt% of inorganic filler iron powder, 1.5 wt% of thixotropic agent calcium sulfate whisker and 2.5 wt% of curing agent Hexamethylene Diisocyanate (HDI) at 90 ℃, and reacting for 2h to prepare the biodegradable adhesive.
Example 6:
step 1: adding 168.7g (1.5mol) of lactic acid with the mass concentration of 80%, 15.2g (0.1mol) of glycolic acid with the mass concentration of 50%, 45.6g (0.4mol) of caprolactone, 5.4g (0.06mol) of 2, 3-butanediol, 2g (0.01mol) of polypropylene glycol 200 and 0.8g of zinc acetate into a reactor, raising the temperature of an oil bath to 190 ℃ under the protection of nitrogen for reaction for 3 hours, then vacuumizing, gradually increasing the vacuum degree, removing trace water and redundant 2, 3-butanediol by decompression, continuing the reaction for 4 hours at 190 ℃ to obtain viscous polylactic acid copolymer polyol, wherein the molecular weight of the polylactic acid copolymer polyol is 3172 by GPC test;
step 2: 166.4g (1.6mol) of malonic acid, 153g (1.7mol) of 2, 3-butanediol and 0.8g of zinc acetate are added into a reactor, under the protection of nitrogen, the oil bath is heated to 190 ℃ for reaction for 3 hours, then the reactor is vacuumized, the vacuum degree is gradually increased, trace water and redundant 2, 3-butanediol are removed under reduced pressure, the reaction is continued for 2 hours at 190 ℃ to obtain viscous polyester polyol, and the molecular weight of the polyester polyol is 3022 by GPC test;
and step 3: uniformly mixing 75 wt% of polylactic acid copolymer polyol, 10 wt% of polyester polyol, 1 wt% of hydrolysis stabilizer 2, 2' -bis (2-oxazoline), 10 wt% of inorganic filler talcum powder, 1 wt% of thixotropic agent calcium sulfate whisker and 3 wt% of curing agent Hexamethylene Diisocyanate (HDI) at 90 ℃, and reacting for 2h to prepare the biodegradable adhesive.
Comparative example 1:
step 1: adding 168.7g (1.5mol) of lactic acid with the mass concentration of 80%, 35.4g (0.3mol) of 3-hydroxypentanoic acid, 5.3g (0.07mol) of 1, 2-propanediol and 0.8g of zinc acetate into a reactor, heating the mixture in an oil bath to 190 ℃ under the protection of nitrogen, reacting for 4 hours, then vacuumizing, gradually increasing the vacuum degree, reducing the pressure to remove trace water and redundant 1, 2-propanediol, and continuing to react for 5 hours at 190 ℃ to obtain viscous polylactic acid copolymer polyol, wherein the molecular weight of the polylactic acid copolymer polyol is 2883 by GPC test;
step 2: 177g (1.5mol) of succinic acid, 121.6g (1.6mol) of 1, 2-propylene glycol and 0.9g of stannous octoate are added into a reactor, under the protection of nitrogen, the oil bath is heated to 175 ℃ for reaction for 4 hours, then the reactor is vacuumized, the vacuum degree is gradually increased, trace water and redundant 1, 2-propylene glycol are removed under reduced pressure, the reaction is continued for 4 hours at 175 ℃, viscous polyester polyol is obtained, and the molecular weight of the polyester polyol is 2989 by GPC (GPC);
and step 3: 65 wt% of polylactic acid copolymer polyol, 20 wt% of polyester polyol, 1 wt% of hydrolysis stabilizer 1, 3-benzene-bis-oxazoline, 10 wt% of inorganic filler talcum powder, 1 wt% of thixotropic agent fumed silica and 3 wt% of curing agent Toluene Diisocyanate (TDI) are uniformly mixed at 90 ℃ and then react for 2 hours to prepare the biodegradable adhesive.
Comparative example 2:
step 1: adding 112.5g (1mol) of lactic acid with the mass concentration of 80%, 9.1g (0.06mol) of glycolic acid with the mass concentration of 50%, 26g (0.25mol) of 3-hydroxybutyric acid, 3.8g (0.05mol) of 1, 2-propylene glycol and 0.5g of stannous octoate into a reactor, heating the oil bath to 185 ℃ under the protection of nitrogen for reaction for 3 hours, then vacuumizing, gradually increasing the vacuum degree, removing trace water and redundant 1, 2-propylene glycol under reduced pressure, and continuously reacting for 3 hours at 185 ℃ to obtain viscous polylactic acid copolymer polyol, wherein the molecular weight of the polylactic acid copolymer polyol is 2787 by GPC test;
step 2: 80 wt% of polylactic acid copolymer polyol, 1 wt% of hydrolysis stabilizer bis (2, 6-di-isopropyl phenyl) carbodiimide, 14 wt% of inorganic filler talcum powder, 1 wt% of thixotropic agent calcium sulfate whisker and 4 wt% of curing agent Toluene Diisocyanate (TDI) are uniformly mixed at 90 ℃ and then react for 2h to prepare the biodegradable adhesive.
Respectively adding 10 wt% of curing agent Toluene Diisocyanate (TDI) into the biodegradable adhesives prepared in examples 1-6 and comparative example 1, uniformly stirring, placing the biodegradable adhesives in a fixed mold, wherein the mold is a cuboid and is 5cm multiplied by 1cm in size, drying for 2 hours at 80 ℃, preparing a solid or rubber-like sample plate after the biodegradable adhesives are completely cured, covering the sample plate with gauze, submerging the sample plate in artificial seawater, placing the sample plate in a 60 ℃ drying oven, testing the total mass of the sample plate and the gauze at 10 days, 1 month, 3 months and 6 months respectively, calculating the weight loss rate of the sample plate, and drying for 24 hours in a vacuum drying oven at 40 ℃ before weighing. The results are shown in table one:
wherein, the weight loss ratio of the sample plate is calculated according to the following formula:
in the formula:
c, after drying, the mass sum of the sample plate and the gauze is g;
b-mass of blank gauze, g;
a-initial mass of the template, g.
TABLE 1 degradation Properties of biodegradable Adhesives of examples 1-6 and comparative example 1
Experimental results show that the biodegradable adhesive prepared by the invention can be slowly degraded in artificial seawater, and the degradation speed gradually becomes fast along with the prolonging of time; the degradation speed has a certain relation with the addition amount of glycolic acid during copolymerization, and the larger the addition amount is, the faster the artificial seawater degradation speed is; wherein, the powder left in the gauze after the artificial seawater immersion for 6 months may be added inorganic materials and curing agents which cannot be degraded. The biodegradation adhesive without glycolic acid is degraded in artificial seawater much slowly.
The biodegradable adhesives prepared in examples 1 to 6 and comparative example 2 were used to prepare degradable tapes, respectively, using biaxially oriented polylactic acid films as substrates. The tape properties were tested according to the standard YZ/T0160.2-2017 (sealing tape for postal industry: biodegradable tape). Wherein the initial adhesion test is to detect the maximum steel ball size that an adhesive surface with a specified length can be adhered to according to an inclined surface rolling ball method in the national standard GB/T4852-2002. The permanent adhesion force is measured by the failure time of the adhesive tape according to the method for testing the adhesive tape to the standard test steel plate in the national standard GB/T4851-2014; the peel strength is measured according to the 180-degree peel test of the adhesive tape and the stainless steel plate in the national standard GB/T2792-2014.
TABLE 2 Properties of biodegradable adhesive tapes of examples 1 to 6
Experimental results show that the biodegradable adhesive prepared by the invention takes a bidirectional stretched polylactic acid film as a base material to prepare the biodegradable adhesive tape, and the initial adhesive force (ball number) of the prepared biodegradable adhesive tape is more than or equal to 13; the permanent viscosity is more than or equal to 6 h; the 180-degree peel strength is more than or equal to 3 (N/cm); compared with the comparative example 2, the biodegradable adhesive tape prepared by adopting the pure lactic acid and the mixture thereof has the advantages that the initial adhesion, the permanent adhesion and the 180-degree peel strength are improved to a certain extent, particularly the permanent adhesion is greatly improved, so that the biodegradable adhesive containing the polyester polyol can be suitable for various base materials, and the application range of the biodegradable adhesive is expanded.
Many other changes and modifications can be made without departing from the spirit and scope of the invention. It is to be understood that the invention is not to be limited to the specific embodiments, but only by the scope of the appended claims.
Claims (16)
1. A preparation method of a biodegradable adhesive is characterized by comprising the following steps:
step 1: under the action of a catalyst, carrying out esterification and polycondensation reaction on lactic acid and a mixture thereof and a polyol compound at the temperature of 140-220 ℃, under the protection of nitrogen, steaming out generated byproduct water at normal pressure, and then removing trace water and redundant polyol compound under vacuum pressure until the acid value of a synthesized product is lower than 5mgKOH/g to obtain polylactic acid copolymer polyol; the reaction time is 4-12 h;
step 2: under the action of a catalyst, carrying out esterification and polycondensation reaction on a polybasic acid compound and a polyol compound at the temperature of 140-220 ℃, under the protection of nitrogen, steaming at normal pressure to remove generated byproduct water, and then, removing trace water and redundant polyol compound under vacuum pressure until the acid value of the synthesized product is lower than 5mgKOH/g to obtain polyester polyol; the reaction time is 4-12 h;
and step 3: uniformly mixing polylactic acid copolymer polyol, polyester polyol, a hydrolysis stabilizer, an inorganic filler, a thixotropic agent and a curing agent at the temperature of 80-100 ℃, and then continuously reacting for 1-4 hours to obtain the biodegradable adhesive;
1-95 parts of polylactic acid copolymer polyol; 5-95 parts of polyester polyol; 0.1-2 parts of hydrolysis stabilizer; 1-45 parts of inorganic filler; 0.5-2 parts of thixotropic agent; 0-8 parts of a curing agent;
in the step 1, the mixture of the lactic acid and the mixture thereof comprises one or more of glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, butyrolactone, valerolactone and caprolactone; wherein the molar ratio of lactic acid to the mixture is (0.6-1): (0-0.4).
2. The method of claim 1, wherein the mixture of lactic acid and its mixture in step 1 comprises aliphatic alkyd and aliphatic lactone.
3. The method for preparing biodegradable adhesive according to claim 1, wherein the polyol compound in step 1 comprises aliphatic polyol compound and polyether polyol.
4. The method of claim 3, wherein the polyol compound in step 1 comprises one or more of ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, 1, 2-butylene glycol, 1, 3-butylene glycol, 1, 4-butylene glycol, pentanediol, neopentyl glycol, hexanediol, isohexylene glycol, trimethylolpropane, pentaerythritol, polyethylene glycol 200, polyethylene glycol 400, polypropylene glycol 400, and polypropylene glycol 800.
5. The method for preparing biodegradable adhesive according to claim 1, wherein the molar ratio of lactic acid and mixture thereof to polyol compound in step 1 is (1-60): 1.
6. The method for preparing the biodegradable adhesive according to claim 1, wherein the catalyst in the step 1 comprises one or more of zinc acetate, diethyl zinc, stannous octoate, stannic oxide, stannous chloride, tetrabutyl titanate, antimony trioxide, ethylene glycol antimony and antimony acetate; the dosage is 0.01-2wt% of the mass of the lactic acid and the mixture thereof.
7. The method for preparing biodegradable adhesive according to claim 1, wherein the polybasic acid compound in step 2 is one or more of oxalic acid, malonic acid, succinic acid, adipic acid and terephthalic acid.
8. The method of claim 1, wherein the polyol compound in step 2 comprises an aliphatic polyol compound and a polyether polyol.
9. The method of claim 8, wherein the polyol compound in step 2 comprises one or more of ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, 1, 2-butylene glycol, 1, 3-butylene glycol, 1, 4-butylene glycol, pentanediol, neopentyl glycol, hexanediol, isohexylene glycol, trimethylolpropane, pentaerythritol, polyethylene glycol 200, polyethylene glycol 400, polypropylene glycol 400, and polypropylene glycol 800.
10. The method for preparing biodegradable adhesive according to claim 1, wherein the molar ratio of the polybasic acid compound to the polyhydric alcohol compound in step 2 is 1 (1-2).
11. The method for preparing biodegradable adhesive according to claim 1, wherein the catalyst in step 2 comprises one or more of zinc acetate, diethyl zinc, stannous octoate, stannic oxide, stannous chloride, tetrabutyl titanate, antimony trioxide, ethylene glycol antimony, and antimony acetate; the amount is 0.01-2wt% of the mass of the polybasic acid compound.
12. The method for preparing a biodegradable adhesive according to claim 1, wherein the hydrolysis stabilizer in step 3 is one or more selected from bis (2, 6-diisopropylphenyl) carbodiimide, polycarbodiimide, phenyl glycidyl ether, bisphenol a bisglycidyl ether, triglycidyl isocyanate, 2' -bis (2-oxazoline), 1, 3-benzene-bisoxazoline and styrene-epoxy resin copolymer.
13. The method for preparing a biodegradable adhesive according to claim 1, wherein the inorganic filler in step 3 is one or more of quartz powder, aluminum powder, iron powder, talc powder, titanium dioxide, calcium carbonate and barite powder.
14. The method for preparing a biodegradable adhesive according to claim 1, wherein the thixotropic agent in step 3 is one or more of acetylene black, organic bentonite, fumed silica, hydrogenated castor oil and calcium sulfate whiskers.
15. The method for preparing biodegradable adhesive according to claim 1, wherein the curing agent in step 3 is one or more selected from the group consisting of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, an adduct of toluene diisocyanate and trimethylolpropane, toluene diisocyanate dimer, and hexamethylene diisocyanate trimer.
16. A biodegradable adhesive, characterized by being prepared according to the preparation method of any one of claims 1 to 15.
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